We always size a frame according to its "reach measurement" too, simply because we know we prefer running 100-110mm stems. Knowing the frames reach makes proper fitting way-easy.
Look at it this way:
If you built three 54.5cm / 150mm headtube frames - one with a 73-degree seat-tube, another with a 73.5 and the third, with a 74-degree tube; each frames reach will differ quite a bit even though each is considered a size 54.5cm, perhaps forcing you to run an "other" length stem.
That's why many fitters still prefer the frame "reach", rather then "ETT" alone. "ETT's" still a neccessary factor, though.
It would be great if every "off-the-shelf" bike company would include it in their geometry specs - so much easier.
If I were building a frame today with new stuff, I would have to take into account a bit more than yesteryear. Bars are wider, integrated brake levers to me look pretty different from the various mfgs., at least as to where my hand would land and fit, and handlebar reach from the mount sure do appear as they can be all over the place as to throw forward.